Three-dimensional (“3D”) printing is a technique that is starting to gain significant attention and commercial interest. However, to date, 3D printing has been limited to components such as plastic parts and metal lines, as well as to specific plastics, passive conductors, and a few biological materials. A significant advance would be the ability to 3D print functional active electronic materials and devices in a variety of geometries, beyond the two dimensional (“2D”) constraints of traditional microfabrication semiconductor processing. Developing the ability to 3D print various classes of materials possessing distinct properties could enable the freeform generation of active electronics in unique functional, interwoven architectures. Achieving seamless integration of diverse materials with 3D printing is a significant challenge that requires overcoming discrepancies in material properties in addition to ensuring that all the materials are compatible with the 3D printing process.
The freeform generation of active electronics in unique architectures which transcend the planarity inherent to conventional microfabrication techniques has been an area of increasing scientific interest. Three-dimensional large-scale integration (3D-LSI) can reduce the overall footprint and power consumption of electronics, and is usually accomplished via stacks of two dimensional semiconductor wafers, in which interconnects between layers are achieved using wire-bonding or through-silicon vias. Overcoming this “2D barrier” has significant potential applications beyond improving the scalability in semiconductor integration technologies. For instance, the ability to seamlessly incorporate electronics into three-dimensional constructs could impart functionalities to biological and mechanical systems, such as advanced optical, computation or sensing capabilities. For example, integration of electronics on otherwise passive structural medical instruments such as catheters, gloves, and contact lenses are critical for next generation applications such as real-time monitoring of physiological conditions. Such integration has been previously demonstrated via meticulous transfer printing of pre-fabricated electronics and/or interfacing materials via dissolvable media such as silk on nonplanar surface topologies. An alternative approach is to attempt to interweave electronics in three dimensions from the bottom up. Yet, attaining seamless interweaving of electronics is challenging due to the inherent material incompatibilities and geometrical constraints of traditional micro-fabrication processing techniques.